Processing methods for providing metal-comprising materials within high aspect ratio openings

ABSTRACT

In one aspect, the invention includes a processing method, comprising: a) providing a substrate having a high aspect ratio opening therein; b) forming a metal-comprising layer over the opening; c) providing a first pressure against the metal-comprising layer; and d) ramping the pressure that is against the metal-comprising layer to a second pressure at a rate of from about 1 atmosphere per second about 100 atmospheres per second. In another aspect, the invention includes a processing method, comprising: a) providing a substrate having a high aspect ratio opening therein, the opening having a widest portion and a width at said widest portion; b) in a first chamber, sputter depositing a metal to form a metal-comprising layer over the opening, the metal-comprising layer having a thickness that is at least about twice the width of the opening; c) transferring the substrate to a second chamber having a first pressure therein; and d) while the substrate is within the second chamber, ramping the pressure within the second chamber at a rate of at least about 20 atmospheres per second to a second pressure.

This application is a continuation of Ser. No. 09/900,116 filed Jul. 6,2001 now U.S. Pat. No. 6,537,903, which is a continuation of 09/191,931filed Nov. 13, 1998 now U.S. Pat. No. 6,274,253.

TECHNICAL FIELD

The invention pertains to methods of forming metal-comprising materialswithin openings, and has particular utility for methods of formingmetal-comprising materials within openings having aspect ratios ofgreater than or equal to about 6:1.

BACKGROUND OF THE INVENTION

Continuing goals in semiconductor fabrication processes are to decreasethe amount of semiconductor wafer real estate consumed by electricalcomponents, and to decrease the amount of semiconductor wafer realestate consumed by electrical interconnects between components. A methodof reducing real estate consumed by electrical components andinterconnects is to form the components and interconnects withinvertical openings having high aspect ratios. For purposes ofinterpreting this disclosure and the claims that follow, a high aspectratio opening is defined as an opening having an aspect ratio of greaterthan or equal to about 6:1.

Electrical components and interconnects can comprise metal-comprisingmaterials, such as, for example, aluminum, aluminum alloys, tungsten, ortitanium. It is difficult to provide such metal-comprising materialsuniformly within high aspect ratio openings. For instance, if it isattempted to deposit such metal-comprising materials into a high aspectratio opening, the materials will frequently form a bridge over theopening, rather than filling the opening. Methods have been developedfor pushing bridging material into an opening by applying asubstantially static high pressure to the material to drive it into theopening. Such methods work acceptably for openings having aspect ratiosof less than 6:1, but frequently will not adequately drivemetal-comprising materials into openings having aspect ratios greaterthan or equal to 6:1. Accordingly, it is desired to develop alternativemethods for providing metal-comprising materials within high aspectratio openings.

SUMMARY OF THE INVENTION

In one aspect, the invention encompasses a method of providing ametal-comprising material in a high aspect ratio opening. A substratehaving a high aspect ratio opening extending therein is provided. Ametal-comprising layer is formed over the opening. A first pressure isprovided against the metal-comprising layer. The pressure against themetal-comprising layer is ramped to a second pressure at a rate of fromabout 1 atmosphere per second to about 100 atmospheres per second toforce the metal-comprising layer into the opening.

In another aspect, the invention encompasses a method of providing ametal-comprising material in a high aspect ratio opening. A substratehaving a high aspect ratio opening extending therein is provided. Theopening has a widest portion and a width at said widest portion. A metalis sputter-deposited in a first chamber to form a metal-comprising layerover the opening. The metal-comprising layer has a thickness that is atleast about twice the width of the opening. The substrate is transferredto a second chamber having a first pressure therein. While the substrateis within the second chamber, the pressure within the second chamber isramped at a rate of at least about 20 atmospheres per second to a secondpressure to force the metal-comprising layer into the opening.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a fragmentary, diagrammatic, cross-sectional view of asemiconductor wafer fragment at a preliminary processing step of amethod of the present invention.

FIG. 2 is a view of the FIG. 1 wafer fragment shown at a processing stepsubsequent to that of FIG. 1.

FIG. 3 is a view of the FIG. 1 wafer fragment shown at a processing stepsubsequent to that of FIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8)

A processing method of the present invention is described with referenceto FIGS. 1-3. Referring to FIG. 1, a semiconductor wafer fragment 10comprises a substrate 12 having an opening 14 formed therein. Substrate12 can comprise, for example, monocrystalline silicon lightly doped witha p-type conductivity enhancing dopant. Alternatively, substrate 12 cancomprise, for example, an insulative material, such as silicon dioxideor borophosphosilicate glass (BPSG). To aid in interpretation of theclaims that follow, the term “semiconductive substrate” is defined tomean any construction comprising semiconductive material, including, butnot limited to, bulk semiconductive materials such as a semiconductivewafer (either alone or in assemblies comprising other materialsthereon), and semiconductive material layers (either alone or inassemblies comprising other materials). The term “substrate” refers toany supporting structure, including, but not limited to, thesemiconductive substrates described above.

Opening 14 extends to an electrical node 16. Electrical node 16 cancomprise, for example, a conductively doped diffusion region within asemiconductive substrate 12, or a metal layer within an insulativesubstrate 12.

Opening 14 preferably comprises a high aspect ratio (i.e., an aspectratio of equal to or greater than about 6:1). Also, opening 14 comprisesa critical dimension, which is defined as a minimum width across theopening. For example, opening 14 can comprise a circular horizontalcross-sectional shape, with a diameter corresponding to the criticaldimension. Opening 14 will have a preferred high aspect ratio if it hasa depth that is at least about six times greater than its criticaldimension.

Referring to FIG. 2, a metal-comprising layer 18 is provided oversubstrate 12, and over opening 14. Layer 18 can be deposited by, forexample, sputter deposition. Metal-comprising layer 18 can comprise, forexample, elemental aluminum, aluminum alloys, or other conductivemetallic materials, such as for example, materials comprising silver orcopper. Preferably, the metallic materials of layer 18 have a meltingtemperature of less than or equal to about 1500° C. If layer 18comprises elemental aluminum, or aluminum alloys, layer 18 is preferablyprovided over a layer of titanium nitride. Such layer of titaniumnitride can be formed by, for example, chemical vapor deposition toextend over substrate 12 and within opening 14. An advantage ofproviding titanium nitride beneath an aluminum-comprising layer is thatthe titanium nitride can function as a “glue layer” to assist inadhering the aluminum-comprising layer to substrate 12. Also, a layer oftitanium can be formed beneath the layer of titanium nitride. Anadvantage of providing titanium under the titanium nitride is that thetitanium can provide a good electrical connection to node 16.

Occasionally, as shown, a portion 20 of the material of layer 18 entershigh aspect ratio opening 14. In many instances, a substantial portionof opening 14 remains void of the metal-comprising material of layer 18.Instead of filling high aspect ratio opening 14, layer 18 forms a bridgeover the opening.

Metal-comprising layer 18 has a thickness “A.” Also, opening 14comprises a width. If opening 14 is not cylindrical, the opening cancomprise a plurality of different widths, with one of the widthscorresponding to a widest portion of opening 14. If opening 14 iscylindrical, the width will be equivalent throughout opening 14 and willbe equal to a diameter of the cylindrical opening 14. For purposes ofinterpreting this disclosure, the “widest portion” of a cylindricalopening is defined as a diameter of the opening. Most preferably,thickness “A” is greater than the width of opening 14 at the widestportion of opening 14. Such relationship of the thickness ofmetal-comprising layer 18 to a width of opening 14 enables layer 18 tocompletely fill opening 14 when it is forced within the opening.Preferably, thickness “A” is at least about twice a critical dimensionof the width of opening 14.

Referring to FIG. 3, a bridging portion of metal-comprising layer 18 isforced within opening 14. Such forcing occurs by providing wafer 10within a reaction chamber having a first pressure againstmetal-comprising layer 18, and increasing the pressure at a rate of fromabout 1 atmosphere per second to about 100 atmospheres per second to asecond pressure. The second pressure is then maintained for a time offrom about 1 second to about 120 seconds. Metal-comprising layer 18 isdriven within opening 14 during either the ramping of the pressure, orthe maintaining of the second pressure. Preferably, water fragment 10will be maintained at a temperature of from about 400° C. to about 500°C., and more preferably at about 480° C., during the ramping of pressureand the maintaining of the second pressure. The first pressure againstmetal-comprising layer 18 can comprise, for example, 1 atmosphere. Thesecond pressure against metal-comprising layer 18 can comprise, forexample, a pressure of from about 600 atmospheres to about 1000atmospheres, and preferably comprises a pressure of about 700atmospheres. A suitable device for accomplishing the above-describedprocessing conditions is described in article entitled A 3-Level, 0.35micrometer interconnection process using an innovative high pressurealuminum plug technology, by Z. Shterenfeld-Lavie, et. al., from theJun. 27-29, 1995 VMIC Conference (1995 ISMIC).

A preferred rate at which a pressure against metal-comprising layer 18is ramped varies according to the dimensions of opening 14. If opening14 comprises an aspect ratio of less than 7:1, the pressure againstmetal-comprising layer 18 is preferably ramped at a rate of at leastabout 20 atmospheres per second. On the other hand, if opening 14comprises an aspect ratio of greater than 10:1, the pressure againstmetal-comprising layer 18 is preferably ramped at a rate of greater thanor equal to 35 atmospheres per second.

In preferred methods of the present invention, metal-comprising layer 18is forced into opening 14 at a sufficient rate that opening 14 is filledwithin a period of less than 2 seconds, and more preferably a period ofless than 1 second, from a time that a pressure ramp against layer 18 isinitiated. Example conditions for accomplishing such preferred fillingof an opening 14 comprising a depth of less than or equal to about 2.4microns and a critical dimension of greater than or equal to about 0.35microns is a ramp rate of greater than or equal to about 20 atmospheresper second. If opening 14 comprises a depth of less than or equal toabout 3 microns and a critical dimension of greater than or equal toabout 0.25 microns, a preferred ramp rate is greater than 35 atmospheresper second. If opening 14 comprises any of (1) a depth of less than orequal to about 4 microns and a critical dimension of greater than orequal to about 0.35 microns; (2) a depth of less than or equal to about2 microns, and a critical dimension of greater than or equal to 0.15microns; or (3) a depth of less than or equal to about 1 micron and acritical dimension of greater than or equal to about 0.1 microns, thepressure against metal-comprising layer 18 will preferably be ramped ata rate of at least about 35 atmospheres per second.

In an exemplary embodiment of the invention, metal-comprising layer 18is formed by sputter deposition in a first reaction chamber. The wafercomprising fragment 10 is then transferred to a second reaction chamberwherein the wafer is placed in an ambient which is non-reactive withexposed portions of substrate 12, and non-reactive with exposed portionsof metal-comprising layer 18. A suitable ambient is, for example, anambient consisting essentially of argon. A pressure within the secondreaction chamber is then ramped at a rate of at least about 20atmospheres per second to force metal-comprising layer 18 into an highaspect ratio opening within substrate 12.

The method of the present invention can advantageously fill openingshaving high aspect ratios with a metal-comprising layer in times of 120seconds or less. While not intended to be bound by any particularmechanism, it is suggested that the process by which metal-comprisinglayer 18 is forced into high aspect ratio opening 14 can comprise asolid transfer process. Specifically, it is suggested that a temperatureat an interface of substrate 12 and metal-comprising layer 18 mayincrease rapidly during a rapid pressure ramp of the present invention.Processing conditions of the present invention are preferably adiabatic,such that a temperature within a processing chamber comprising wafer 10is expected to increase approximately linearly with pressure due to therelationship expressed by the ideal gas equation (the temperature willincrease exactly linearly with pressure if the gases within the chamberbehave as ideal gases). The ideal gas equation is PV=nRT, wherein P ispressure, V is volume, n is the moles of gas, R is a gas constant(8.3144 Joule/K-mole), and T is temperature.

As the temperature increases, a localized temperature gradient can formsuch that a thin portion of metal-comprising layer 18 adjacent theinterface with substrate 12 can melt to form a lubricating liquid film.The lubricating liquid film can then enable the bridge ofmetal-comprising layer 18 to slip into opening 14. It is noted thatchemical analysis of a portion of metal-comprising layer 18 forcedwithin opening 14 reveals that the vast majority of metal-comprisinglayer 18 within opening 14 has not melted during the forcing intoopening 14. In fact, there is generally no indication of a melted andre-solidified portion of metal-comprising layer 18 within opening 14.Such, however, does not preclude the above-discussed mechanism whereby avery thin portion of metal-comprising, layer 18 melts to form a verythin lubricating surface.

It is advantageous that the vast majority of metal-comprising layer 18does not melt and re-solidify upon its transfer into opening 14. Suchmelting and re-solidification could adversely affect conductivity andother physical properties of the portion of metal-comprising layer 18forced within opening 14.

After metal-comprising layer 18 is forced within high aspect ratioopening 14, subsequent processing (not shown) can be utilized toincorporate metal-comprising layer 18 into integrated circuitry as, forexample, either an electrical interconnect or an electrical component.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

What is claimed is:
 1. A semiconductor processing method, comprising:providing a semiconductor substrate having an electrical node, and ahigh aspect ratio opening extending to the node; forming an adhesionlayer within the opening; forming a metal-comprising layer bridge acrossthe opening; and exposing the metal-comprising layer bridge to apressure ramp rate of from about 1 atmosphere per second to about 100atmospheres per second to transfer metal of the metal-comprising layerfrom the bridge into the opening.
 2. The method of claim 1 wherein themetal-comprising layer comprises one or more metals selected from thegroup consisting of aluminum, copper and silver.
 3. The method of claim1 wherein the opening extends through an electrically insulativematerial.
 4. The method of claim 1 wherein the adhesion layer comprisestitanium nitride and the metal-comprising layer contains aluminum. 5.The method of claim 4 further comprising forming titanium within theopening prior to forming the adhesion layer.
 6. The method of claim 1wherein the ramping rate is greater than 10 atmospheres/second.
 7. Themethod of claim 1 wherein the substrate is maintained at a temperatureof from about 400° C. to about 500° C. during the exposure to thepressure ramp rate, and wherein the metal-comprising layer has a meltingtemperature of less than or equal to 1500° C.
 8. The method of claim 1wherein a pressure on the metal-comprising layer bridge ramps from about1 atmosphere to at least 800 atmospheres during the exposure to thepressure ramp rate.
 9. A semiconductor processing method, comprising:providing a semiconductor substrate having an electrical node, and ahigh aspect ratio opening extending to the node; forming ametal-comprising bridge across the opening, the metal of the bridgecomprising one or more of aluminum, silver and copper; and exposing themetal-comprising bridge to a pressure ramp rate of from about 1atmosphere per second to about 100 atmospheres per second to transfermetal from the bridge into the opening.
 10. The method of claim 9wherein the ramping rate is greater than 10 atmospheres/second.
 11. Themethod of claim 9 wherein the substrate is maintained at a temperatureof from about 400° C. to about 500° C. during the exposure to thepressure ramp rate and wherein the metal-comprising bridge has a meltingtemperature of less than or equal to 1500° C.
 12. The method of claim 9wherein the opening has a widest portion and a width at said widestportion, and wherein the metal-comprising bridge has a thickness overthe opening that is at least twice the width at the widest portion ofthe opening.
 13. The method of claim 9 wherein the forming themetal-comprising bridge comprises sputter deposition.
 14. The method ofclaim 9 wherein the substrate comprises monocrystalline silicon, and thenode comprises a conductively-doped diffusion region within themonocrystalline silicon.
 15. The method of claim 9 wherein the apressure against the metal-comprising bridge ramps from about 1atmosphere to at least 600 atmospheres during the exposure to thepressure ramp rate.
 16. A semiconductor processing method, comprising:providing a semiconductor substrate having an electrical node, and anopening extending to the node; depositing a metal-containing bridgeacross the opening; and exposing the bridge to a pressure ramp rate offrom about 1 atmosphere per second to about 100 atmospheres per secondto transfer metal from the bridge into the opening.
 17. The method ofclaim 16 wherein the ramping rate is greater than 10 atmospheres/second.18. The method of claim 16 wherein the substrate is maintained at atemperature of from about 400° C. to about 500° C. during the exposureto the pressure ramp rate and wherein the bridge has a meltingtemperature of less than or equal to 1500° C.
 19. The method of claim 16wherein the opening has a widest portion and a width at said widestportion, and wherein the bridge has a thickness over the opening that isat least twice the width at the widest portion of the opening.
 20. Themethod of claim 16 wherein the bridge comprises at least one ofaluminum, copper and silver.
 21. The method of claim 16 wherein thesubstrate comprises monocrystalline silicon, the node comprises aconductively-doped diffusion region within the monocrystalline silicon,the bridge comprises aluminum, and an adhesion layer is formed withinthe opening prior to depositing the bridge.
 22. The method of claim 16wherein the a pressure against the bridge ramps from about 1 atmosphereto at least 600 atmospheres during the exposure to the pressure ramprate.